Re: Chou cam 4912

["M.Stein" <matthias@gom.com>]

Hello Enzo!

On Tue, 9 Jan 2001, Enzo Pascale wrote:

> Hi Matthias,
> 
> Thanks a lot for the configuration file. Now it works.
> 
> I have now one more problem using UMB buffers.
> 
> When I snap a frame to a single UMB buffer it works well, but I need
> to snap different frames to different buffers. 
> So I tried to snap several frames, to consecutive buffers
> and something weird happened.
> 
> The first frame in the first buffer was ok, but the frames stored in
> the second, third, ... buffer were slightly corrupted. Like if few
> pixels were placed in a wrong position.
> 
> Then I went to check umb buffers and what I found out is that the
> image dimensions are right while the size  was not what I would
> expect:
> 
> GIOC_GE_GET_UMBWIDTH and  GIOC_GE_GET_UMBBUFSIZE return the right
> value 512X480 but 
> GIOC_GE_GET_UMBBUFSIZE returns 249856 bytes like if the frame was
> 512X488. (each pixel is 8 bit deep).
> 
> I did the same check without using UMB and now 
> GIOC_GE_GET_MEMWIDTH, GIOC_GE_GET_MEMHEIGHT, GIOC_GE_GET_MEMBUFSIZE
> all return the right value: 512, 480 and 245760. And the frame was clear.
> 
> Do you have any idea of what is going on?
> 
> Thanks again,
> 
>        Enzo.
> 

After each frame a structure called iti_info_t (see itifgExt.h) was
appendend. This holds mainly the image time stamp and some statistics.
After appending this structure, the size was rounded up to the PAGE_SIZE
size of the system, to make the things a little bit easier (mmap and
stuff).
So if you are working with umb-buffers, please use UMBBUFSIZE to calculate
the offset to the second image (not width * height * depth)!

Remark: There is also a ioctl GET_UMBBUFADDR to get the offset address of
        the buffer specified with SET_UMBBUF.
 
						matthias

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